B-starch is produced in substantial amounts in the conventional flour processing in starch and glucose factories by mixing the flour with water to give a dough having from 25% to 40% of dry substance and separating it to its components by centrifugation after a maturing period; cf. G. Tegge, xe2x80x9cStxc3xa4rke und Stxc3xa4rkederivatexe2x80x9d, Behr Verlag (publishers), 1984.
The phase of the dough having the highest specific gravity, the so-called A-starch, can be separated from the dough by decantation, purified from fiber fragments in rotary screens, and washed in hydrocyclones.
The gluten, which has a lower specific gravity, is obtained in an agglomerated form as a further phase of the dough and is separated from the dough after the separation of the A-starch, for example, by sieve bends, or even prior to the separation of the A-starch by decantation in extractors. The simultaneous separation of A-starch and gluten in three-phase decanters is also known.
In addition to the so-called B-starch, the third phase of the dough, after the separation of the A-starch and gluten, contains the soluble components of flour, namely albumins, globulins, pentosanes, ashes, soluble carbohydrates, etc. On a microscopical scale, B-starch consists of conglomerates of starch granules, which are mostly rather small, with proteins, hemicelluloses, fibers and the like. Therefore, as compared with A-starch, B-starch has a lower specific gravity.
To date, B starch has been processed in various ways. Thus, after dehydrating on cylinder dryers, it has often been processed into so-called swell-starch flour which is used as a feed component or as an inexpensive thickener. If the B-starch is dehydrated by centrifugation prior to drying, the soluble components of the flour are lost with the waste-water stream.
Another possibility for utilizing B-starch is the complete enzymatic saccharification of the starch fractions obtained to yield glucose, followed by concentration by evaporation. In this process, the Maillard reaction gives rise to dark-brown colored syrups, which are in turn suitable as raw materials for a wide variety of fermentation methods or as binders. One possibility for this digestion is direct fermentation into alcohol.
It has also been tried to treat B-starch enzymatically or chemically in such a way that as pure as possible a starch fraction can be separated. Thus, for example, part of the B-Starch conglomerates are cleaved by hemicelluloses, proteinases or aqueous sodium hydroxide, so that pure starch granules are released, and the viscosity of the third phase of dough separation is reduced. Due to their higher specific gravity and the reduced viscosity in their environment, the starch granules can in turn be separated by centrifugation. Due to its relatively high purity, the starch fraction thus obtained can be combined with A-starch for certain processing applications. Thus, the yield of A-starch is increased. The minor contaminants present in the additional starch thus produced do not affect the further processing into glucose syrup, for example, or do so but slightly, for example, by resulting in an increased refining expenditure.
One drawback of these methods is the substantial devaluation of the non-starch fraction of the third phase of dough separation. Products are obtained which have a bad taste and are so rich in ashes that they can only be mixed into pig food or dried onto fodder bran. Thus, a drawback of all methods known to date is that substantial fractions of per se valuable components are obtained in a minor quality and actually cannot be utilized, but must be disposed of.
Thus, it has been the object of the invention to provide a process for the enzymatic processing of the third phase of dough separation in which all components of the third phase of dough separation, if possible, are obtained in a high quality and are therefore well utilizable, so that they are obtained in an economically and ecologically valuable form and need no longer be disposed of.
This object is achieved by adding, after the usual mechanical separation of A starch and gluten, amylases and hemicellulases to the third phase of dough separation containing B-starch and the soluble flour components, immediately heating it at temperatures of from 55 to 75xc2x0 C., preferably 60 to 70xc2x0 C., and immediately concentrating it by evaporation following saccharification and pentosane partial hydrolysis.
Preferably, the method is performed by selecting the quantities of the added enzymes and the reaction conditions to obtain a balanced ratio of glucose, dextrines and residual starch.
Further, the reaction conditions are selected such that the Maillard reaction occurs as little as possible or not at all.
Finally, the reaction conditions will preferably be selected such that the soluble proteins of the third phase of dough separation are not altered and that as little as possible microbial fermentation occurs.
The process products thus obtained can be used as a partial or complete substitute of raw materials made from skimmed milk or vegetable carbohydrates in animal feeds, especially in feeds for young animals, and in food products, especially in spray-dried products, sweets or ices.